The present disclosure is generally related to polymer nanoparticles. More particularly, the present disclosure provides polymer nanoparticles comprising tri-block copolymer chains that form a particular formation or shape.
Over the past several years, polymer nanoparticles have attracted increased attention not only in the technical fields such as catalysis, combinatorial chemistry, protein supports, magnets, and photonics, but also in the manufacture of rubbery products such as tires. For example, nanoparticles can modify rubbers by uniformly dispersing throughout a host rubber composition as discrete particles. The physical properties of rubber such as moldability and tenacity can often be improved through such modifications. Moreover, some polymeric nanoparticles may serve as a reinforcement material for rubber. For example, polymer nano-strings are capable of dispersing evenly throughout a rubber composition, while maintaining a degree of entanglement between the individual nano-strings, leading to improved reinforcement over traditional reinforcing fillers.
However, an indiscriminate addition of nanoparticles to rubber may cause degradation of the matrix rubber material. Rather, very careful control and selection of nanoparticles having suitable architecture, size, shape, material composition, and surface chemistry, etc., are needed to improve the rubber matrix characteristics. For example, properties of polymeric nanoparticles made from diblock copolymer chains are controlled by the thermodynamics of diblock copolymers in a selected solvent. The thermodynamic phase diagram of those systems usually depends on two factors, the volume fractions of the components (φi, i=1, 2, 3 . . . ) and the miscibility between them (χijNi parameter between components). Therefore, for a given system, i.e., when the χijNi parameters between components are fixed, the formation of micelle structures depends primarily on the volume fraction of each component (φi, i=1, 2, 3 .  . . ). In order to obtain a micelle nanoparticle of desired structure, the concentration or the volume fraction must be controlled. Flexibility of concentration adjustment is usually small due to the underlying thermodynamic laws and the phase diagrams. As such, it cannot provide high flexibility in concentration variations. This could raise unwelcome constraints in industrial processes.
Advantageously, the present disclosure provides a disk-like nanoparticle including a core layer that comprises a cross-linked multi-vinyl substituted aromatic hydrocarbon and a shell layer that comprises tri-block copolymer chains, each having a first, a second, and a third block. The first and third blocks of the tri-block copolymer chains comprise a vinyl aromatic monomer and are crosslinked with the core. The second block comprises a conjugated diene monomer units and comprises the top and bottom axial surfaces of the disk-like nanoparticle. The weight ratio of the monomer comprising the first block and third block to the monomer comprising the second block is 1:1 to 100:1.
A rubber composition comprising a rubber matrix and the disk-like nanoparticle disclosed above is also provided. A tire comprising the rubber composition is also described herein.
A method for making a disk-like nanoparticle in a liquid hydrocarbon medium is also provided. The nanoparticle has a core layer and a shell layer, the shell layer comprises tri-block copolymer chains having a first block, a second block, and a third block. The method comprises the steps of: polymerizing conjugated diene monomers with a multi-functional lithiated amine containing initiator, wherein the initiator is a hydrocarbon solvent soluble, anionic polymerization multi-lithio amine initiators that comprises at least two or more lithio amines in one molecule and has the general formula:
wherein Q is (a) an element selected from the group consisting of O, S, N, P and Si or (b) an alkylene group having from 1 to 20 methylene groups, and R1 and R2 are the same or different and are selected from the group consisting of alkyls, cycloalkyls and aralkyls containing from 1 to 20 carbon atoms; copolymerizing vinyl aromatic monomers to form the first and third blocks, thereby producing the tri-block copolymer chains; assembling the tri-block copolymer chains in the liquid hydrocarbon medium to form micelle structures; and crosslinking a multiple-vinyl-substituted aromatic hydrocarbon with the tri-block copolymer chains in the micelle structures to form a cross-linked core and to form polymer nanoparticles.
A disk-like nanoparticle produced from the method described above is also presented.
In another embodiment, a disk-like nanoparticle includes a core layer comprising a cross-linked multi-vinyl substituted aromatic hydrocarbon, and a shell layer comprising A-B-C tri-block copolymer chains, each having a first, a second, and a third block. The first block of the A-B-C tri-block copolymer chains includes a vinyl aromatic monomer and is crosslinked with the core. The second block includes a conjugated diene monomer, and the third block comprises the top and bottom axial surfaces of the disk-like nanoparticle. The disk-like nanoparticle further includes a residue of a multi-functional lithiated amine-containing initiator, wherein the initiator is a hydrocarbon solvent soluble, anionic polymerization multi-lithio amine initiators that comprises at least two or more lithio amines in one molecule and has the general formula:
wherein Q is (a) an element selected from the group consisting of O, S, N, P and Si or (b) an alkylene group having from 1 to 20 methylene groups, divalent and R1 and R2 are the same or different and are selected from the group consisting of alkyls, cycloalkyls and aralkyls containing from 1 to 20 carbon atoms.